I've seen a couple of activity advent calenders now, and I have to admit, it was something I had never heard or thought of, but it is now on the cards for using our advent calender next year (this year it has Christmas decorations for Princess' tree) :)

Build a Lego Christmas tree? We are Lego mad in our house at the moment.

Is there anywhere near you taking food donations for Christmas? Our local shopping centre management does a big food drive in December. Last year and the year before Annie and I went around Coles and she chose breakfast, lunch and dinner food (non perishable) for one family for Christmas.

You could do that on a smaller scale. Or donate food to the local animal shelter so the animals have something special for Christmas too.

I love all your ideas so far. We used to go Christmas light hunting in the days before houses were lit up, and it was only the Christmas trees in the front window - but it would still work now... just start driving and and "THERE'S ONE!"